Yes
Yes, they Are Bmx Bikes. I Do Not Recommend Them Thought.
Yes
The Mongoose Rebel Is a 20" Freestyle Bmx Bike
No. a 9T sprocket will only fit a cassette hub, and not freewheel hubs.
It will if you have bmx (or bmx style) cranks.
Yes its a fantastic bike and great for tricks
change out the hub
the easiest way is to go to your local bike shop
If you want a cheap bike mine as well go for a mongoose
You can get a 9 tooth sprocket, you will need a conversion kit to do it. Haro makes a decent one just do a search for Haro 25/9
well that movie was shot back in 1983 mongoose was one of the top bmx bikes of the time so my best guess would have to be a1983 mongoose supergoose by the way the bike looked in the movie or it was a mongoose motomag they both looked practically alike hope this helped